Resistance for electrical uses.



PATENTED JUNE 28, 1904.

J. F. TRACY. RESISTANGE FOR ELECTRICAL USES.

APPLICATION FILED DEC. 12, 1903.

N0 MODEL.

FIGJ.

WITNESSE S: KW

UNITED STATES Patented June 28, 1904:.

PATENT OFFICE.

JAMES F. TRACY, OF SHERIDANVILLE, PENNSYLVANIA, ASSIGNOR OF ONE-HALF TOWILLIAM H. McFADDEN, OF PITTSBURG, PENNSYL- VANIA.

RESISTANCE FOR ELECTRICAL USES.

SPECIFICATION forming part of Letters Patent No. 763,812, dated June 28,1904.

i Application filed December 12, 1903. Serial No, 184,949. (No model.)

To all whom, it may concern.-

Be it known that I, J AMES F. TRACY, a citizen of the United States,residing at Sheridanville, in the county of Allegheny and State ofPennsylvania,have invented or discovered certain new and usefulImprovements in Resistances for Electrical Uses, of which improvementthe following is a specification.

The invention described herein relates to certain improvementsinresistances for electrical purposes, the improvements being especiallyapplicable for use in connection with starting-boxes for motors,circuit-controllers, heaters, &c.; and the-invention has for its 01 jecta construction capable of presenting any desired resistance withoutdestruction or material injury to the resistance mechanism or partscontrolled thereby.

The invention is hereinafter more fully described and claimed.

In the accompanying drawings, forming a part of this specification,Figure 1 is a side elevation of a starting-box embodying my improvement.Fig. 2 is a sectional elevation of the same on a plane indicated by theline II II, Fig. 1; and Fig. 3 is a transverse section on a planeindicated by the line III III, Fig. 1.

In applying my improvement to startingboXes a holder or shell 1, formedof a suitable insulating material, as indurated fiber asbestos, &c., isfilled with finely-comminuted material 2. This material may be formed ofany suitable substance, as cast-iron, steel,

wrought-iron, &c., or a mixture of two or more materials which whencomminuted will give the desired resistance. Contact-pieces 8 aresecured upon the holder or shell at suitable distances apart andelectrically connected to the core 2. A convenient construction to thisend consists in providing the contacts with jaws 1, embracing the shelland secured in position'by pins 5, passing through the jaws, the shellor holder, and the core, the material of the latter being compacted, bypreference, so as to make good contact with the pins 5. The movablecontact is formed by a U-shaped spring 6, having one leg sccured to asliding block 7, movably mounted on a guide-rod 8, arranged parallelwith the shell or holder. The other leg of the contactspring is adaptedto bear against the contacts in succession as the supporting-block isshifted. It is preferred to secure the guide-rod 8 to the brackets 9,whereby the tubular shell or holder is secured to a suitable support. Bymovably mounting the block 7 on the rod or the latter in its bearing theblock may be swung around for repairs, &c., ot' the spring or otherpart. Ordinarily one terminal, 10, of the starting-box is formed on orby the last one of the series, while the other terminal, 11, iselectrically connected to the rod 8, which is electrically connectedthrough the slide 7 to the contact-spring. It will be understood thatthe terminal 10 may be connected to any one of the contacts 3, dependentupon the resistance required. In case the comminuted material shouldbecome inoperative or defective, the plugs 12 at the end of the holdercan be removed and the comminuted material discharged and new materialplaced in the holder.

I have found that with my improved starting-box ashunt-wound motor canbe started when fully loaded without any injury to the motor orstarting-box. A similar test made with the form of starting-box of theconstruction now in use resulted in the burning out of all theresistance-coils.

lVhile I have found that finely-comminuted cast-iron gives good results,the invention is not limited to such material, as I consider theemployment or use of any comminuted material or mixture ofcomminutedn1aterials,many of which will suggest themselves to those skilled in theart, capable of giving the desired resistance effect as within the scopeof my invention.

I claim herein as my invention 1. A starting-box having in combination anon-conducting tubular holder or shell, a core formed of comminutedconducting material, a series of contacts arranged in the shell orholder, and electrically connected to the core, ed to bear on thecontact-pieces, substantially and a contact movable along the stationaryas set forth. 1 contacts, substantiallyas set forth. In testimonywhereof I have hereunto set 2. A starting-box having a tubular shell, amy hand. filling of comminnted conducting material, JAMES F. TRACY.contact-pieces provided With jaws gripping Witnesses: the shell andelectrically connected to the fill- DARWIN S. WoLooTT,

ing, and a sliding block having a spring adapt- F. E. GAITHER.

